QR code not decoded every time

[TomSAVU]

I have a VI and four images of the same QR code, taken from different angles.
I succeeded to read the data only from the second image and sometimes from the first one, but never from the last two.
The cell size is around 30 pixels in all images.

What's strange is that, for second picture, it works with minimum cell size 20 or even 30, but doesn't work with minimum cell size 15.

Can anybody give me some help, please?

[rolfk]

We have found that the IMAQ Vision barcode detection routines are very picky about lightning, angle and sharpness of an image. The same barcodes always were detected without a single hitch by Halcon. Even less quality images where the lines look barely distinguishable by the bare eyes can still be recognized by Halcon with high confidence, while IMAQ Vision has long before declared complete defeat.

IMAQ Vision was once a pretty good product but it has unfortunately not received substantial improvements in the last 15 or more years. In the meantime the competition has overtaken it left and right and IMAQ Vision plays in a sub par league now.

Of course packages like Halcon do cost money and in the same range as the entire LabVIEW Professional Developer suite. But if you need a fast and reliable image processing library it really can be worth the money. Full LabVIEW integration is however not available and developing that yourself is a tedious and expensive project. 

[TomSAVU]

Would it be any image processing that could help?

I am now looking at Zbar, but my application needs to know the corners' x-y coordinates, and the Python functions of Zbar are giving only the left, top, width, height data.

[rolfk]

You know a rextangle can be defined by either the corner coordinates as well as one corner and height and width? And one can be computed from the other! So not sure what your question is.

[TomSAVU]

If the rectangle has its axis parallel with the coordinates axis, yes, but in my images the rectangle is rotated.
The images are taken by a camera mounted on a robot arm.

[drjdpowell]

Your problem is you don't have a large enough "quiet zone".  Most barcodes require an empty border zone, and QR codes have quite a big zone: see https://www.qrcode.com/en/howto/code.html.

 

[TomSAVU]

Thanks a lot drjdpowell, I didn't know about this!

With a quiet zone is working a little bit better, indeed, but there are still images which are not recognized.